This invention relates generally to gas turbine engines and more particularly to a weep plug for recovering oil used to lubricate the bearings of a gas turbine engine.
Gas turbine engines typically include a core having a compressor for compressing air entering the core, a combustor where fuel is mixed with the compressed air and then burned to create a high energy gas stream, and a pressure turbine which extracts energy from the gas stream to drive the compressor. In aircraft turbofan engines, a low pressure turbine located downstream from the core extracts more energy from the gas stream for driving a fan. The fan provides the main propulsive thrust generated by the engine.
Bearings are used in the engine to accurately locate and rotatably mount rotors with respect to stators in the compressor and high and low pressure turbines of the engine. The bearings are enclosed in oil-wetted portions of the engine called sumps.
In order to prevent overheating of the bearings, lubricating oil and seals must be provided to prevent the hot air in the engine flowpath from reaching the bearing sumps, and lubricating oil flows must be sufficient to carry away heat generated internally by the bearings because of their high relative speed of rotation.
Oil consumption arises from the method used to seal the engine sumps. The sealing method makes it necessary for an air flow circuit to exist that flows into and out of the sumps. This flow ultimately contains oil that is unrecoverable unless adequately separated and delivered back to the sumps. In one particular configuration the forward engine sump is vented through the forward fan shaft and out the engine through a center vent tube. Once the air/oil mixture exits the sump, it swirls, depositing oil on the inside of the fan shaft. Oil that is contained in the air/oil mixture is lost when it is unable to centrifuge back into the sump through the vent hole due to rapidly escaping vent air.
Some designs allow for oil recovery by using weep holes, which are passages whose function is to provide a dedicated path for oil to re-enter the sump, integrated into the forward fan shaft design. Weep holes are typically smaller in diameter and longer in length than holes designed to route vent flow. However, in other designs, the fan shaft has no dedicated weep holes, only vent holes. Forming weep holes in fan shafts of the latter design after their manufacture and installation in an engine would be prohibitively expensive.
Accordingly, there is a need for a method to recover oil in existing sump structures without modifying the existing hardware.
The above-mentioned need is met by the present invention, which provides a weep plug having a central vent passage and one or more weep passages parallel to the central passage.
The present invention and its advantages over the prior art will become apparent upon reading the following detailed description and the appended claims with reference to the accompanying drawings.